LONG-RANGE COUPLING IN YBA2CU3O7-DELTA (Y1-XPRX)BA2CU3O7-DELTA MULTILAYERS/

YBa2Cu3O7-delta/(Y1-xPrx)Ba2Cu3O7-delta multilayers have been used to probe coupling through (Y1-xPrx)Ba2Cu3O7-delta alloys. We observe that the coupling between ultrathin YBa2Cu3O7-delta layers, 12 or 24) Angs trom thick, survives through several hundred Angstrom of (Y1-xPrx)Ba(2 )Cu(3)O(()7-delta with x=0.4 and 0.55. T-c versus the thickness of the spacer-alloy, and activation energies for flux motion, with fields pa rallel and perpendicular to the c-axis, have been used to probe this l ong range coupling. All these experiments point to an unusually large coupling length for these two alloy compositions. In the x=0.55 case t his result is particularly surprising since the alloy material display a semiconducting behaviour for this composition. T-c measurements, ac tivation energies, and a study of the vortex dynamics in these coupled multilayers is presented along with new results obtained on a series of multilayers built with a more insulating alloy, x=0.7.